Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deposits [Abstract]
Brokered money market accounts	$ 289,031	$ 208,348
Demand and other noninterest-bearing	5,081,901	3,944,495
Interest-bearing demand	1,265,212	985,293
Money market	2,543,712	1,791,283
Savings	861,941	723,667
Certificates of deposit less than $100,000	286,791	304,830
Total core deposits	10,039,557	7,749,568
Certificates of deposit greater than $100,000	100,399	79,424
Certificates of deposit insured by CDARS®	25,374	22,039
Other brokered certificates of deposit	78,481	0
Subtotal	10,532,842	8,059,379
Deposits, Valuation Adjustment From Acquisition Accounting	(757)	36
Total deposits	10,532,085	8,059,415
Deposit Liabilities Reclassified as Loans Receivable	1,600	$ 4,400
Time Deposits, Fiscal Year Maturity [Abstract]
2016	338,958
2017	74,177
2018	34,727
2019	20,857
2020	12,600
Thereafter	9,726
Total	$ 491,045